1. Field of the Invention
The present invention relates to an electronic display, and particularly to a luminous billboard using a light emitting diode as a light source.
2. Description of Related Art
Billboards can be divided into non-luminous billboards or luminous billboards. The non-luminous billboards without light source cannot provide a visual advertisement at night or darksome environment. The conventional luminous billboards make use of cold cathode fluorescent lamp (CCFL) as light source. However, the CCFL has many disadvantages such as large volume, low light efficiency, short life span and polluted to the environment so that the CCFL can not be widely used in billboards.
Light emitting diodes (LEDs), on the other hand, have many advantages, such as high luminance, low power consumption, highly compatible with integrated circuits, long-term reliability, environmental friendliness and are becoming widely used as light source, as described in an article entitled “Solid-State Lighting: Toward Superior Illumination” cited in a publication of Proceedings of the IEEE, Vol. 93, No. 10, October, 2005 authored by Michael S. Shur.
Accordingly, what is desired, therefore, is a billboard using LED as light source with a compact size, environment friendliness and long-term reliability.